The present invention relates generally to valve indicators, and more particularly to a valve indicator for visually and/or electronically indicating the position of a valve shaft.
Various electrical and mechanical position indicators are used to indicate the position of pneumatic or hydraulic lift valves. Switches are activated in respective end positions of the valve stroke, creating an electrical signal for open and closed-valve positions. The signal can then be transmitted to a control unit. Similarly, visual indication can also be provided to display the open and closed positions of the valve.
FIGS. 1A-1C illustrate some of the electrical and/or visual solutions for providing linear position indication for a valve. FIG. 1A illustrates a principle used in the art for providing electrical indication of the position of a valve stem. The valve stem 10 has an adapter 12 attached. The adapter 12 activates a first switch 20 when the valve stem 10 is at a position where the valve is closed. The first switch 20 is adjustable along a fixed shaft 22. Thus, moving switch 20 along the shaft 22 changes the position for indicating a closed-valve. A shaded area 24 represents the area in which a closed-valve position can be adjusted.
The adapter 12 activates a second switch 30 when the valve stem 10 is at an open position. The second switch 30 also adjustable along a fixed shaft 32. Thus, moving the switch 30 along the shaft 32 changes the position for indicating an open-valve. A shaded area 34 indicates the area in which the open-valve position can be adjusted and the switch 30 is triggered. With the present arrangement, however, providing visual indication for the position of valves with various stroke lengths is not readily evident.
FIG. 1B illustrates another principle used in the art for providing indication of the position of a valve. Referring to the schematic diagram of FIG. 1B, the apparatus for monitoring valve lift has two adjusters 14 and 16, which activate two limit switches 20 and 30, respectively. The switches 20, 30 act as position sensors for the up and down positions of a drive spindle 12. The present arrangement allows for the adjusters 14 and 16 to be moved so that they activate the limit switches 20, 30 in the open and closed positions for a given valve stroke.
The drive spindle 12 has the same stroke length as the valve stem 10. Hence, the arrangement does not readily offer a solution to provide a visual indicator among valves having different stroke lengths. The visual indicator 40 would have the same display length 42 as the stroke length 18 of the valve stem 10. Therefore, the visual indicator 40 would display different amounts of visual area for valves having different stroke lengths.
FIG. 1C illustrates yet another principle used in the art for providing indication of the position of a valve. The valve stem 10 has an adapter 12 attached. An adjuster 14 activates a first switch 20 when the valve stem 10 is at a closed-valve position. The adjuster 14 is adjustable along adapter 12. A shaded area 24 represents the area in which the closed-valve position can be adjusted and the switch 20 is triggered.
Another adjuster 16 activates a second switch 30 when the valve stem 10 is at an open-valve position. The adjuster 16 is adjustable along adapter 12. Thus, moving the adjuster 16 along the adapter 12 changes the position for indicating an open-valve. A shaded area 34 represents the area in which the open-valve position can be adjusted and the switch 30 is triggered.
With the present arrangement, a visual indicator 40 for indicating the position of the valve would have an indication length 42 that is equal to the stroke length 18 minus the separation H between the two adjusters 14, 16. Thus, it is not clear how a single visual indicator could be adapted to the present arrangement for use on valves with various stroke lengths.
The present invention is directed to providing a visual and electrical indicator for valves with various lengths of valve strokes.
In view of the foregoing and other considerations, the present invention relates to an apparatus for visually and/or electronically indicating the position of a valve shaft.
In accordance with one aspect of the present invention, there is provided an apparatus for indicating a state of a valve. The valve has a stem being movable in closing and opening directions between closed and open valve positions. The apparatus includes a first cam system being biased in the opening direction. The first cam system is capable of adjustably engaging the stem when the stem is adjacent to the closed valve position and is movable by the stem in the closing direction once engaged. The apparatus also includes a second cam system being integral to or separate from the first cam system and being biased in the closing direction. The second cam system is capable of adjustably engaging the stem when the stem is adjacent to the open valve position. The second cam system is movable by the stem in the opening direction once engaged. The apparatus includes an indicator moveable by the first and the second cam systems. The indicator is capable of indicating at least open, intermediate, and closed states of the valve.
In accordance with another aspect of the present invention, there is provided an apparatus for visually and electronically indicating a state of a valve. The valve has a stem being movable in closing and opening directions between closed and open valve positions. The apparatus includes a first cam system, a first switch, a second cam system, a second switch, and an indicator. The first cam system includes a first adjustable member engaging the stem when the stem is adjacent to the closed valve position. The first cam system is movable by the stem in a closing direction once engaged. The first cam system also includes a first biasing member forcing the first cam system in the opening direction. The first switch is capable of being actuated by the first cam system when the stem is at the closed valve position. The second cam system is integral to or separate from the first cam system. The second cam system includes a second adjustable member engaging the stem when the stem is adjacent to the open valve position. The second cam system is movable by the stem in the opening direction once engaged. The second cam system also includes a second biasing member forcing the second cam system in the closing direction. The second switch is capable of being actuated by the second cam system when the stem is at the open valve position. The indicator is moveable by the first and the second cam systems and is capable of indicating at least open, intermediate, and closed states of the valve.
In accordance with yet another aspect of the present invention, there is provided a method for indicating states of a valve having a stem. The stem is movable in closing and opening directions between closed and open valve positions. The method includes the steps of: adjusting a first cam system to engage the stem adjacent the closed valve position and adjusting a second cam system to engage the stem adjacent the opened valve position. The method also includes indicating a closed-valve state by displacing the first cam system in the closing direction with the stem to the closed valve position and indicating an open-valve state by displacing the second cam system in the opening direction with the stem to the opened valve position. The method also includes indicating an intermediate-valve state in the absence of engagement of the stem with the first and second cam system by biasing the first cam system in the opening direction and biasing the second cam system in the closing direction.
The foregoing summary is not intended to summarize each potential embodiment, or every aspect of the invention disclosed herein, but merely to summarize the appended claims.